simple change chart in VBA

[LKnomad]

I am trying to make a simple change to a single selected chart in a word document using VBA. I cannot seem to make this work. Any help appreciated.

The code that I have been trying looks like this:

 
Sub ChangePieChart()
 
Dim objshape as chart
  
 objshape.Height = 250 
     
End Sub

This should be so simple but I cannot figure it out. I get a variety of errors when I try different options.